The present invention concerns a method for the casting of one concrete product or of several concrete products placed side by side at the same time by means of one casting machine as sliding casting out of high-consistency concrete mix, the concrete mix being fed by means of one feed member or by means of several feed members placed side by side into one or several separate cross sections of a concrete product to be cast. The concrete mix being compacted by reducing the free spaces present between the aggregate particles in the concrete mix. The invention further concerns a slide-casting machine for casting of one or several concrete products placed side by side, said slide-casting machine provided with walls which form one or several cross sections of a concrete product to be cast as well as with one or several feed members placed side by side for feeding the concrete mix as well as with members for compacting of the concrete mix.
When products are manufactured out of concrete or of a corresponding material by using a casting machine of the extruder type, which is characterized in the use of feed screws and of compacting members that constitute extensions of same for the purpose of compacting the mix, one of the main problems consists of how to ensure and control uniform compacting of the section to be cast.
It has been possible to eliminate the problem to some extent by, based on experience, regulating the mutual ratio of the speeds of rotation of the parallel feed screws with invariable transmission ratios. However, wear of the feed members and variations in the properties of the mix alter the nature of the casting process and the compacting in the casting process constantly
In the Finnish Patent No. 70,821 a slide-casting method for casting of hollow slabs out of concrete is described. Concrete mix is fed onto the casting base by means of a screw spiral that becomes thicker towards its final end. The mix is compacted further by means of a mobile mandrel fitted after the feed screw, whereby the mandrel, which moves relative an articulation point, produces a shearing-compacting effect. The movement of the feed screws also makes the casting machine itself move forward on the base.
From methods of extrusion of plastic products it is known to measure the axial force acting upon the feed screw or the pressure of the molten plastic and to regulate the speed of rotation of the feed screw on that basis. Such a method for casting of plastic is described, e.g., in the U.S. Pat. Nos. 3,704,972 and 3,090,992 as well as in the Swiss Patent No. 387,289. However, when a homogeneous plastic mix is being cast, a change in the speed of rotation of the feed screw does not affect the compacting pressure, but by means of its regulation the output of the machine is affected.
In the British Pat. No. 1,586,181 a slide-casting machine is described in which the wheels mounted underneath the machine are connected to the drive mechanism so as to carry the machine on the casting base. The transfer output fed to the wheels is regulated on the basis of the torque or forces acting upon the feed screw. In this way the compacting effect of the feed screws in the direction of running of the machine can be made as uniform as possible. In the apparatus it is, however, not possible to regulate the compacting separately in different points of the same cross section.
In studies and in practical casting processes it has been noticed that the compacting process requires two main components: EQU pressure +vibration or EQU pressure +shear-compacting effect.
In particular when a so-called high-consistency concrete mix is used, the pressure component has a very high significance.
This high significance of the pressure component makes it possible to employ said pressure component for the control of the entire compact process.